"Limbs contain muscles, bone, cartilage, blood vessels, tendons, ligaments and nerves — each of which has to be rebuilt and requires a specific supporting structure called the matrix."

It's the matrix that has been missing from the current transplant procedure.

Ott's team found a way to strip living cells from a donor organ and "repopulate" the remaining structure — or matrix — with the progenitor cells that would grow the new tissues.

The decellularization technique has been used to regenerate kidneys, livers, hearts and lungs from animal models, but the MGH team thinks this is the first time it's been used for the more complex tissues of a bioartificial limb.

They stripped the cells from the forearms of dead rats, then injected vascular cells into the main artery and muscle cells into the muscle receptors. When later transplanted onto recipient rats, the limbs filled with blood, and electrical stimulation of the muscles flexed the animals' paws. The researchers want to try baboon forearms next.